Byoung-Jo "J" Kim(IEEE S’93 - M’98) received his B.S. from Seoul National University, Korea in ’93, M.S. in ’95 and Ph.D. from Stanford University in ‘97 all in Electrical Engineering. He had worked and consulted for several wireless start-up companies in the Silicon Valley before joining the Mobile Wireless Network Research Group in AT&T Labs-Research in early '98. From '93 until '99, he worked on Physical and System level technologies for wireless communications, including radio propagation, signal processing, and system-level engineering. His current research interests are WMANs, WLANs, wireless access, mesh network, mobile networking and computing, especially mobility management, wireless security, wireless network management, wireless/wireline QoS, and 'open' approaches for cross-layer optimization from physical to applications layers. The major theme of his research is to combine the advancement of Wireless Systems research in Electrical Engineering and that of Mobile Networks/Applications research in Computer Engineering. His recent projects cover 802.11, 802.16 & WiMAX technologies, multi-network interface, multi-domain mobility, wireless security,radio resource management, next-generation mobile network architecture, and related industry standard activities. He is also interested in evolutionary biology, genetic programming, and wonders of nature.

This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in 2013. , Volume 51, Issue 9, 2013-09-01, 10.1109/MCOM.2013.6588652

{As the number of wireless users and per-user bandwidth demands continue to increase, both the vendor and carrier communities agree that wireless networks must evolve toward more dense deployments. So-called “heterogeneous networks” are a commonly proposed evolution, whereby existing macro-cellular networks are supplemented with an underlay of small cells. The placement of new small-cell sites is typically determined based on various location-dependent factors such as radio propagation calculations, user densities, and measurements of congestion and demand. The backhaul network, which can account for a significant portion of the total cost of the deployment, is then designed in reaction to the placement of small cells. In contrast, we describe a design method which first considers the locations of existing fibered and powered facilities that might be leveraged to provide inexpensive backhaul. Naturally, such a method is only feasible if the carrier has a legacy local fiber network. This paper describes an efficient fiber backhaul strategy for a small-cell network, which leverages facilities associated with an existing fiber-to-the node (FTTN) residential access network. Once potential small-cell sites are determined from among all FTTN remote terminals (RTs), optimization techniques are used to choose the most efficient subset of sites for maximum coverage, and to design the fiber backhaul architecture. }

This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in 2012. , 2013-02-24

{As more wireless systems are deployed in many new environments with different antenna heights, frequency bands, and multipath conditions, there are increasing demands for making more channel measurements to better understand wireless propagation and assist deployment engineering. We design and implement a rapid wireless channel sounding sys- tem using the Universal Software Radio Peripheral (USRP) platform and GNU Radio software to address these demands. Our approach incorporates the simultaneous measurement of channel propagation characteristics from multiple transmitters. The system consists of multiple battery-powered reference signal transmitters and battery-powered receivers that can discriminate the transmitters. This enables the rapid set-up of the channel sounder at a field location and expedited measurements by analyzing multiple reference signals during a single walk or drive through the environment. In this paper, we describe our initial design and implementation of this rapid channel sounding system. We expect that the proposed approach, with a few further refinements, can transform the propagation measurement as a routine part of day-to-day wireless network engineering.}

{Despite the extraordinary success of the cellular mobile telecommunications industry, many of the underlying design strategies and service assumptions that have served us arguably well over the past four decades may benefit from a fresh new look. Even today’s LTE (Long-Term Evolution), which is designed to meet the demands of modern broadband Internet packet connectivity, nonetheless draws heavily on the legacy of cellular’s circuit-oriented origins. Its heavy reliance on fine-grained tunnels and hard-state signaling protocols, for example, imposes performance penalties and cost burdens that may not be inevitable if hard-earned lessons are incorporated in the coming years. In this paper we describe a fresh approach to cellular network architecture. Inspired by past and present ideas and experiences by others and ours, we propose fundamental principles to guide the development of efficient and flexible network architecture, able to serve the still-unknown needs and preferences of future users. We offer an example of a network built on those principles and suggest how we can manage the evolution from today’s networks to an architecture better suited to the decades ahead.}

The definitive version was published in proceedings of OFC 2011 (Optical Society of America). , 2011-03-06

{The wireline backhaul of cellular networks plays a critical role in connecting cells to the rest of the telecom world and to each other. As the radio and air interfaces have evolved, so too has the backhaul. The architectures and transport technologies used for wireless backhaul in the US will be described.}

{We propose to demonstrate to the audience of Mobicom '03 a new approach for transparently enhancing mobile networking and application support mechanisms. Until now, such features have required support from the host operating system (OS). The host OS typically is closed and/or proprietary, and this is especially the case for host OS that is dominant in the market. The centerpiece of our new approach is an intelligent network interface card in a CF-to-PCMCIA converter from factor, which we call the "AT&T Intelligent Network Card" or "iCard" [1,2]. previously released: TD-5NNHGH }

{Internet Roaming is an IP-based corporate data network architecture that provides convenient secure mobile networking across office WLANs, residential WLANs, public WLANs, and cellular data networks for corporate wireless data users. It has three building blocks: the IRC (Internet Roaming Client), the SMG (Secure Mobility Gateway), and the VSA (Virtual Single Account) server. Working with an SMG and a VSA server, an IRC can present a single sign-on authentication interface for a user to initiate a secure connection to a corporate intranet via the best available wireless network, and maintain the secure connectivity thereafter as the user moves from one wireless network to another. As a proof of concept, a software-based prototype system has been developed, which enables a Windows-based computer to seamlessly roam between WLANs attached to different subnets while maintaining an encrypted connection to a Windows-based SMG. A hardware-based IRC that looks like a network interface card is also under development. It can provide secure mobile networking for a variety of mobile devices such as PDAs. The measurements of handoff speed of the software-based prototype system and comparisons between Internet Roaming and other WLAN/cellular integration methods are also given in this paper. }

{The IEEE 802.11 standard specifies both radio and MAC protocol design. We observe that its CSMA protocol helps avoid much of co-channel interference at the potential expense of degraded network throughput in a large multi-cell WLAN network. Due to the coupling between the physical and MAC layers, conventional frequency planning and allocation methods for typical cellular networks cannot be applied directly to the 802.11 network. In this paper, by focusing on interactions among access points based on their traffic loads and radio propagation, we formulate the channel assignment for the 802.11 network as a 0-1 programming problem, where one version of the problem is shown to be NP-complete. In light of computational complexity, a heuristic algorithm is proposed and analyzed. The algorithm is then applied to two cellular settings with known optimal assignments. For one of the settings, the proposed technique generates the optimal channel assignment. As for the second case of a large network, although only a suboptimal solution is obtained by the algorithm, it is shown to be excellent. Therefore, as the 802.11 networks are widely deployed, the proposed method can serve as a valuable tool for frequency planning of large-scale multi-cell WLAN networks. patent pending 11/08/2001 HB84C0000-020815-05TM paper was not published at IEEE ICC 2003, May 11-15 2003; Anchorage, AK; Copyright re-issued to IEEE VTC Fall 2003. }

{This paper presents results from an experimental survey of user experience for data applications in future cellular wireless networks. Using a network emulator, we tested a variety of network scenarios with different channel sharing schemes (dedicated and shared bandwidth), computing models (local processing with remote files and thin-client server based computing), applications (Web browsing, Word, PowerPoint), and devices (laptops and Palm devices). Subjective quality ratings (1 to 5) from 100+ users were collected to generate an average quality score for the user experience in each scenario. We quantify the degradation of user experience with lower bit rates and a larger number of users sharing the channel. We also find that users have a marked preference between local and thin-client computing based on bandwidth conditions and applications. Publisher: IEEE Pub/Conf: SAINT'01 }

A method and apparatus to enable IP networking for mobile hosts without requiring changes to be made to the TCP/IP stack in the operating system installed on the mobile hosts. The apparatus is an "intelligent device" that can be installed on or connected to a mobile host, and may comprise a software-only logical module, physical hardware, or a combination of both. To a mobile host, the intelligent device emulates a network interface such as an Ethernet card or a telephone modem. The intelligent device appears to an access network just like any regular IP host connected to the access network through a physical network interface device. The intelligent device handles all mobile networking functions for the mobile host, and may control multiple different physical network interface devices to enable a connection to the "best" access network available to the mobile user at his location.

A system for determining a location of a receiver is disclosed. The system includes at least one transmitter transmitting one or more radio signals, respectively. The system also includes a receiver comprising a clock, a memory, and a processor configured to execute computer-executable instructions stored in the memory. The instructions makes the receiver operable to receive the radio signals, capture the radio signals as one or more received signal waveform, respectively, and store the received signal waveforms in the memory. The instructions also make the receiver operable to calculate one or more virtual transmitted waveforms based upon the received signal waveforms, respectively and determine, based upon the received signal waveforms and the virtual transmitted waveforms, a position of the receiver relative to the transmitters.

A mobile participation platform enables a wireless network operator or third party to solicit response data related to a specific time and location specific event by signaling multiple mobile device users that meet predefined qualifications. The qualifications include presence at the specific location at the specific time, and may include other characteristics, such as prior consent to receive solicitations, and particular device type or data collection functionality. The platform locates mobile devices that may qualify for participation, and generates and transmits a solicitation. Mobile devices receiving the solicitation may activate a participation client to acknowledge the solicitation and to contribute by submitting the requested response data, which may include photos, text, sensor data, audio, video and the like. The qualifications are verified, the response data is validated, and anonymity and privacy are maintained by associating the mobile device and other pertinent non-identifying information with an encrypted identifier.

A USB based USIM or SIM device is disclosed. For example, the device comprises a Subscriber Identity Module (SIM) module, a SIM to Universal Serial Bus (USB) conversion module coupled to said SIM module, and a USB interface module coupled to said SIM to USB conversion module for engaging a computing device.

A frequency planning method for use in an IEEE 802.11 wireless network is described. The frequency planning method obtains traffic load information associated with access points belonging to a multi-cell wireless network and assigns channels to the access points based on the traffic load information.

A method of performing receive antenna selection is presented. The method executes a determination operation for a set of receive antennas, determines a maximum result of the determination operation for two of the antennas, eliminates one of the two antennas from the set of antennas, and repeats the determination and elimination process until only a predetermined number of antennas remain in the set. The signals from these remaining antennas are then processed. The present invention reduces receiver complexity and cost.

A network includes access points that can reduce beacon power to redistribute mobile station loading on the access points. A relatively highly loaded access point can reduce its beacon power so that one or more connected mobile stations will migrate to a further access point covering the migrating mobile station.

A method and apparatus to enable IP networking for mobile hosts without requiring changes to be made to the TCP/IP stack in the operating system installed on the mobile hosts. The apparatus is an "intelligent device" that can be installed on or connected to a mobile host, and may comprise a software-only logical module, physical hardware, or a combination of both. To a mobile host, the intelligent device emulates a network interface such as an Ethernet card or a telephone modem. The intelligent device appears to an access network just like any regular IP host connected to the access network through a physical network interface device. The intelligent device handles all mobile networking functions for the mobile host, and may control multiple different physical network interface devices to enable a connection to the "best" access network available to the mobile user at his location.

System and method to support networking functions for mobile hosts that access multiple networks,
Tue Oct 21 18:13:05 EDT 2008

An IP-based corporate network architecture and method for providing seamless secure mobile networking across office WLAN, home WLAN, public WLAN, and 2.5G/3G cellular networks for corporate wireless data users. The system includes Internet roaming clients (IRCs), a secure mobility gateway (SMG), optional secure IP access (SIA) gateways, and a virtual single account (VSA) server. The IRC is a special client tool installed on a mobile computer (laptop or PDA) equipped with a WLAN adaptor and a cellular modem. It is responsible for establishing and maintaining a mobile IPsec tunnel between the mobile computer and a corporate intranet. The SMG is a mobile IPsec gateway installed between the corporate intranet and the Internet. It works in conjunction with the IRC to maintain the mobile IPsec tunnel when the mobile computer is connected on the Internet via a home WLAN, a public WLAN, or a cellular network. The SIA gateway is a special IPsec gateway installed in the middle of the wired corporate intranet and an office WLAN. It works with the IRC to ensure data security and efficient use of corporate IP addresses when the mobile computer is connected to the office WLAN. The VSA server manages authentication credentials for every corporate user based on a virtual single account concept. The Internet Roaming system can provide secure, always-on office network connectivity for corporate users no matter where they are located using best available wireless networks.

A frequency planning method for use in an IEEE 802.11 wireless network is described. The frequency planning method obtains traffic load information associated with access points belonging to a multi-cell wireless network and assigns channels to the access points based on the traffic load information.

A method and apparatus for integrating Fixed Wireless Broadband Access (FWBA) and a Wireless Local Access radio Network (WLAN) is presented. An antenna or satellite dish leads to an RF (Radio Frequency) processor and modulator/demodulator component installed in a home or business which allows for receipt of an analog and/or digital signal sent by broadband transmission from a fixed base station. Integrated to the FWBA set-up is a transmitter/receiver linking a number of portable or stationary devices in a WLAN, allowing for seamless communication to and from the WLAN devices inside or outside of the home and/or business. Devices can be programmed to receive or transmit data according to location and channel conditions and signal strength inside and outside of the home or business.

A method of performing receive antenna selection is presented. The method executes a determination operation for a set of receive antennas, determines a maximum result of the determination operation for two of the antennas, eliminates one of the two antennas from the set of antennas, and repeats the determination and elimination process until only a predetermined number of antennas remain in the set. The signals from these remaining antennas are then processed. The present invention reduces receiver complexity and cost.

A frequency planning method for use in an IEEE 802.11 wireless network is described. The frequency planning method obtains traffic load information associated with access points belonging to a multi-cell wireless network and assigns channels to the access points based on the traffic load information.

An access interface module includes a first network interface module for interfacing with a first access network and a second network interface module for interfacing with a second access network of a type that is different from the first network. The access module can further include a processor coupled to the first and second network interface modules and a device interface module coupled to the processor for interfacing with a host device.

A method and apparatus to enable IP networking for mobile hosts without requiring changes to be made to the TCP/IP stack in the operating system installed on the mobile hosts. The apparatus is an intelligent device that can be installed on or connected to a mobile host, and may comprise a software-only logical module, physical hardware, or a combination of both. To a mobile host, the intelligent device emulates a network interface such as an Ethernet card or a telephone modem. The intelligent device appears to an access network just like any regular IP host connected to the access network through a physical network interface device. The intelligent device handles all mobile networking functions for the mobile host, and may control multiple different physical network interface devices to enable a connection to the best access network available to the mobile user at his location

A method of performing receive antenna selection is presented. The method executes a determination operation for a set of receive antennas, determines a maximum result of the determination operation for two of the antennas, eliminates one of the two antennas from the set of antennas, and repeats the determination and elimination process until only a predetermined number of antennas remain in the set. The signals from these remaining antennas are then processed. The present invention reduces receiver complexity and cost.